Br or Sr (Sorry don’t know). Taubah is the acknowledgement of doing something that Allah SWT has forbidden. So what we are asking forgiveness for is disobeying Allah SWT when we were aware that we were.
To lack the ability or competence to indulge in that sin, will only, act as a deterrent for you. To still have the ability or competence to indulge in a sin does not mean you necessarily will do it, even if you thought about it.
Your example of becoming paralyzed or say in a vegetative state or maybe brain dead, is a compelling reason why we should never delay our Taubah for sins we commit knowingly or unknowingly, for someday we loose the ability to even recall what we have done or realize it.
Taubah is not accepted once the death rattle reaches ones throat. Its not because the person looses the ability to sin again (well that too) but because things unseen probably become apparent, which in this world, have acted as a deterrent for us from commiting sins. For instance, people who deny the existence of Allah SWT and unseen things, witness those things and it becomes apparent to them, they could not possibly deny it thereafter.